Motion transfer by use of cable provides superior characteristics in pulling and rotation, but obviously flounders in its ability to push unless the cable is rigid or contained. Shielded cables provide a mechanism for pulling and pushing a flexible cable by use of a stationary casing element. However, the shielded cable must be supported at both ends and becomes inefficient if the cable includes any type of bend. These problems are exemplified when a cable is employed in either an intricate setting or large scale operation. For instance, a robotic hand is an intricate device made operational by motion transfer cabling. The shielded cable is impractical for the size of the device and need for extreme bends. Conversely, the unshielded cable must have a level of rigidity, making it limited in its ability to provide motion transfer in both directions.
U.S. Pat. No. 5,080,682, issued to the instant inventor, teaches the use of an artificial robotic hand employing cables for motion transfer, the disclosure is incorporated by reference herein as if fully restated hereinafter. One objective of the '682 Patent is to provide an artificial hand prosthesis having hinged or articulating fingers and a thumb. The device is dependant upon control cables for individual movement of each member. An electric motor is coupled to a linear gear rack which in turn is connected to a stiff cable drawn to the end of the finger. In operation, the motor moves the rack in a forward direction causing the finger to bend along the linkage joints, reversal of the motor causes the finger to straighten. The use of a shielded cable is not cost effective and the severe bending required by the fingers is impractical due to the friction caused by the shield.
Thus, what is needed is a means for transferring torque having articulating members with minimal loss in torque transfer having particular use in robotics and providing a means for large torque transfer using a frictionless lead screw arrangement.